(1) Field of the Invention
The present invention relates to switch arrays and particularly to membrane type keyboards which comprise a switch array. More specifically, this invention is directed to a flat membrane keyboard having a front face with raised key areas and underlying switches which, when actuated, provide tactile feedback to the user. Accordingly, the general objects of the present invention are to provide novel and improved apparatus of such character.
(2) Description of the Prior Art
Recent advances in the field of microelectronics have resulted in a demand for miniaturized keyboards for use in the inputting of data to appliances such as calculators and electronic games. In order to be suitable for widespread use in appliances which include microprocessors, a keyboard must possess certain attributes. These attributes include a high degree of reliability, small size, low cost, uncomplicated construction, ease of key location by the user and the ability to provide the user with tactile feedback which will indicate that the switch contacts associated with an operated key have been closed. While these attributes have been individually achieved in the prior art, there has not previously been a keyboard possessing all of these attributes.
There are, in the prior art, many types of keyboards. The known keyboards include those relatively complex devices having separate actuating key arrangements for the switch array and flat multi-layer devices of the type generally known in the art as "membrane" keyboards. For a general discussion of membrane type keyboards which provide the user with tactile feedback, reference may be had to U.S. Pat. No. 4,245,138. A membrane type keyboard with tactile feedback which includes raised key portions is disclosed in U.S. Pat. No. 4,190,748.
While the keyboards of the referenced patents, and other similar keyboard arrangements, have proven to be exceptionally successful, there has not previously been available a keyboard which incorporates tactility with a convex formed graphic front face so that the separate mechanical keys and elaborate housings required with previous tactile keyboards having raised key locators on the surface were not necessary.